Defloculate, Or Add Water?

[clay lover]

I have a glaze that is too thick and adding water to it in the past made it thin in the final appearance, after firing, but still thick and gloppy, drippy, runs, when dipping.  I watched the you tube videos on the subject, and let it settle, dipped off some water, (clear), and tried adding sodium silicate. I  let it sit a couple of days , and then sieving it to 40 mesh.  There were small rubbery bits all through it, but they did sieve out.   It still is very thick in the bucket, finger marks stay on the surface.  When it sits a day or 2, there is just a bit of water on the top and under that is it homogenous, very fluffy, no thicker in the bottom I/3 of the bucket at all.

Do I add more sodium silicate, or now add some water?

 

F4 feldspar 38

Whiting       14

Zinc Oxide  12

Ball Clay       6

Silica           30

 

copper carb 2

Bentonite     1

 

Thanks for any advice, I have used this glaze for years and just now had this problem.

 

[neilestrick]

First, I recommend always screening through an 80 mesh sieve. 40 will leave a lot of large particles. Second, this glaze is somewhat low in clay content. I like to have at least 10% in my glaze. Because of the low clay content, It will have a tendency to go on less even than other glazes, and show drips more. I would run some tests increasing the ball clay and see if you can get up to 10% or more without affecting the glaze melt. This glaze is off the charts for zinc, and very low in alumina and silica, so getting more clay into it shouldn't hurt.

 

As for your current bucket of glaze, it sounds like maybe you added too much sodium silicate, which will cause the glaze to thicken up. I would try adding more water, but only a little bit at a time.

[clay lover]

Thanks, Neil, I will go work on it.  This glaze was weirdly thick to begin with, I tried the sodium silicate to make it more fluid, but it did not seem to increase the liquidity of it any.

[neilestrick]

Any chance you put way too much bentonite? That would make it gel, too.

[clay lover]

This is a full bucket, made a couple of years ago, It has changed it's behavior during the time I have been using it. ???